<p>Techniques for the efficient ray tracing of animated scenes are presented. They are based on two central concepts: spacetime ray tracing, and a hybrid adaptive space subdivision/boundary volume technique for generating efficient, nonoverlapping hierarchies of bounding volumes. In spacetime ray tracing, static objects are rendered in 4-D space-time using 4-D analogs to 3-D techniques. The bounding volume hierarchy combines elements of adaptive space subdivision and bounding volume techniques. The quality of hierarchy and its nonoverlapping character make it an improvement over previous algorithms, because both attributes reduce the number of ray/object intersections that must be computed. These savings are amplified in animation because of the much higher cost of computing ray/object intersections for motion-blurred animation. It is shown that it is possible to ray trace large animations more quickly with space-time ray tracing using this hierarchy than with straightforward frame-by-frame rendering.</p>